Javaw.exe using 50% cpu when running testclass in JUnit

Greetings all,

I'm a student informatics from Belgium, I'm in my first year and at the moment we're writing simple classes that we have to correct by executing testclasses that we get from our teacher with JUnit. Now, I have a problem with one of the testclasses... When I try to execute it, javaw.exe starts using 50% of my cpu. Also there are 6 test-methods in the testclass and it seems that JUnit gets stuck at the 5th one. When I asked my teacher he had no clue at the moment how to solve this problem or just give an explanation why this problem occurs. My classes have no errors or warnings at all so it's only that one testclass that creates this problem. The project was to make a class to write fractions as 8/5, 7/10, ... and a class that makes a mathematician than can add 2 of those fractions together, multiply 2 of them, and make a fraction more simple (like change 85/5 to 17/1). It's the testclass for the mathematician-class that gives this problem.

Could anyone tell me what I can change/improve in my teacher's testclass so it will work decently and so javaw.exe won't take half of my cpu ? I have added my 2 classes and my teacher's testclass. Thanks in advance.